Somewhat like You Have To Burn The Rope (review here), Achievement Unlocked is less of a game itself and more of a commentary on gaming. Designed by the prolific jmtb02, in Achievement Unlocked, you're presented with a simple playfield; your character is an elephant recycled from Elephant Rave, and he's on a pretty average platformer-looking layout with moving platforms and spikes and so forth. However, there's no goal in the game -- well, no goal in the traditional sense. There are, though, 100 achievements for doing actions from the very simple to the somewhat more complicated.
Anyway, the game is self-consciously silly -- you start racking up achievements from the moment the game is loaded, many without you even having to do anything. The graphics and sounds are pretty simple, while the music is relentlessly cheerful; it gives the game a bit of a circus atmosphere. This is one of the few games where not telling you what the achievements are is defensible -- most of them are pretty easy to figure out from the title, but there are a few tricky ones. Since one of the achievements is to look at the included walkthrough, though, I didn't feel too bad about using it to get the couple I couldn't figure out on my own.
Overall, Achievement Unlocked is good for a silly bit of fun. In some sense, the game is successful, if its goal is to point out how silly achievements in games can be. On the other hand, the achievements in this game are more interesting, varied, and well-thought-out than those in many other games, so it is actually a bit of fun. Perhaps the one departure from realism is that none of the achievements is particularly long or tedious -- you can get all of them without working too hard in less than ten minutes. This perhaps makes the game less realistic, but it also means it can keep being fun. So perhaps in that aspect it's not successful. Still, you'll have fun playing it.